One of the personal stats you have is average time but I feel this isn't as good of a stat as some puzzles will obviously take longer (i.e puzzles with 5 people as opposed to 4) so it skews your average.

I think an easier way of ranking people on time should be by having a cumulative total of second over/under average puzzle time. For example:

Average Puzzle Time: 361 seconds
Your puzzle time: 288Your score: +73

In this situation i got 73 points for finishing 73 second before the average. If on the next puzzle i finish 56 seconds before the average time then my cumulative total would increase to 129. On the next puzzle i get a -19, then my cumulative would then be 110. And so on and so on.

Doing it this way will give a clear cut number which makes it easier to rank people based on time and puzzle difficulty. This scoring prevents people from getting low average times by only picking puzzles with high completion rates(which can also be deemed as easier to solve).